1. (with R. Arcidiacono, A. Solano)
The CT-PPS project
Nicolo Cartiglia
(with R. Arcidiacono, A. Solano)
INFN Torino
On behalf of the CMS and TOTEM Collaborations

2. Table of Contents The CT-PPS Project and its Physics motivations
Experimental Challenges
Constraints on the Tracking Detector
Vertexing and Tracking: expected performances

3. Detector concept
The CMS-TOTEM Precision Proton Spectrometer (CT-PPS) will allow precision proton
measurements in the very forward regions on both sides of CMS during standard LHC running:
Two stations for tracking detectors and
two stations for timing detectors installed
at ~210 m from the common CMS-TOTEM
interaction point (IP5) on both sides of
the central apparatus
LHC magnets between IP5 and the detector stations
used to bend out of the beam envelope protons that have lost
a small fraction of their initial momentum in the interaction
 fractional longitudinal momentum loss (ξ) between 2% and 10%
IP5 p
PPS
210 m
CMS+TOTEM
PPS
IP5
~210m
LHC lattice between IP5 and CT-PPS detector stations

4. The TDR is ready and approved by the two Collaborations
Detector concept
The CMS-TOTEM Precision Proton Spectrometer (CT-PPS) will allow precision proton
measurements in the very forward regions on both sides of CMS during standard LHC running:
Two stations for tracking detectors and
two stations for timing detectors installed
at ~210 m from the common CMS-TOTEM
interaction point (IP5) on both sides of
the central apparatus
LHC magnets between IP5 and the detector stations
used to bend out of the beam envelope protons that have lost
a small fraction of their initial momentum in the interaction
 fractional longitudinal momentum loss (ξ) between 2% and 10%
IP5 p
PPS
210 m
CMS+TOTEM
A Memorandum of Understanding between CERN and
the CMS and TOTEM Collaborations for a common physics program and detector development signed in December 2013
The TDR is ready and approved by the two Collaborations
Now presented to the LHCC (next meeting on Sep. 23rd-25th)
[CERN-LHCC , CMS-TDR-13, TOTEM-TDR-003]

5. Project planning
The CT-PPS project includes an exploratory phase in and a production phase until LHC LS2 (2018)
Exploratory phase ( )
Prove the ability to operate detectors close to the beamline at high luminosity
Show that CT-PPS does not prevent the stable operation of the LHC beams and does not affect significantly the luminosity performance of the machine.
In 2015:
Evaluate RPs in the m region
Demonstrate the timing performance of the Quartic baseline
Use TOTEM silicon strip detectors at sustainable radiation intensity
Integrate the CT-PPS detectors into the CMS trigger/DAQ system.
In 2016:
Evaluate the MBP option
Upgrade the tracking to pixel detectors
Upgrade the timing detectors if required/possible
Data Production phase
Aim at accumulating 100 fb-1 of data before LHC LS2

6. New collimator TCL6 to protect magnet Q6
Roman Pots in LHC line
RP units at: m ~ 215m m  IP5
New collimator TCL to protect magnet Q6
In current plan: detectors housed in Roman Pot, developed by TOTEM
In the exploratory phase of :
- pursue the TOTEM+CMS physics program at low/medium luminosity
- commission RP insertions during high luminosity data taking

7. Experimental Challenges
Position of scattered protons
at 204m, for fixed (ξ,t)
Ability to operate the detectors close to the beam (15-20 s)
Need to sustain very high radiation levels. For 100 fb-1:
proton flux up to 5·1015 cm-2 in the tracker detectors
1012 neq/cm2 and 100 Gy in photosensors and readout electronics
2% < ξ < 10%
Ability to reject background from high PU environment (m = 50), mainly inelastic events overlapping with SD protons from the same bunch crossing
Use proton timing for primary vertex determination Exploit the kinematical constraints of CEP events

8. Detector requirements
Measurement of scattered proton momentum: position and angle in tracking detectors, combined with the beam magnets
Position resolution of μm
Angular resolution much lower than beam angular spread
Slim edges on side facing the beam → dead region ~100 μm
Tolerance to inhomogeneous irradiation
→ ~2·1015 neq/cm2 close to the beam (for 100 fb-1)
Measurement of CEP vertex: proton time on both sides of CMS in timing detectors
Time resolution ~10 ps → Vertex z-by-timing: ~2 mm
Segmentation to cope with the high occupancy expected
Edgeless (~ 200 μm)
Radiation hard
sV ~ 2 mm
5 cm

9. Tracking detectors Baseline: 3D silicon pixel detectors
Detector installation foreseen in 2016
Beam pipe
Flex cables for:
Power
Readout
DSC/SSS
24 mm
16 mm
Redundancy of 6 detector planes per station
16 x 24 mm2 3D silicon pixel sensors
150(x) x 100(y) μm2 pixel pattern
same as CMS pixel detectors
6 PSI46dig readout chips
(52x80 pixels each)
Same readout scheme as Phase-I upgrade of CMS Forward Pixel Tracker

10. 3D sensors Interesting features w.r.t. planar sensors:
3D sensors consist of an array of columnar electrodes
Mature technology after 15 years of R&D and the construction of the ATLAS IBL
Interesting features w.r.t. planar sensors:
Low depletion voltage (~10 V)
Fast charge collection time
Reduced charged trapping probability and
therefore high radiation hardness
Slim edges, with dead area of ~ μm
or Active edges, with dead area reduced to a
few μm
Spatial resolution comparable with planar detectors
3 different 3D sensor layout tested, by FBK, Sintef and CNM:
different in type of columns, sensor edge, electrode configuration

11. FBK 3D sensors Preferred solution: FBK 3D
Passing-through empty columns
Slim edges (200 μm)
Inter-electrode distance 62 mm
Double-sided etching
62.5 μm
New production on the way with:
Double sided etching
100 mm slim edge on one
side of the sensor
New 3E electrode configuration and 2x2 chip modules
x0.8 cm2 Single pixel sensors (1E, 2E, 3E, 4E) [ ]
6 1.6x1.6cm2 Quad pixel sensors CMS (2E, 3E) [ ]
100 mm
155 mm

12. 3D sensors tests
Preliminary results of un-irradiated FBK 3D sensors read out by PSI46dig ROCs, tested at Fermilab with a 120 GeV proton beam
Efficiency vs angle
Edge Efficiency
300 um pixel
200 um edge
Detectors are tilted to reduce the geometrical inefficiency due to the empty electrode columns
Efficiency > 99.5% already at 5o
Efficiency remains high up to 150 μm from the sensor’s boundary
Spatial resolution for 2 pixel clusters : ~12 μm
Measurements with the same detectors, irradiated at fluences from
1·1015 to 1·1016 neq/cm2, were just taken during the last two weeks at Fermilab.

13. 2+2 in-line modules: σ(t)~15 ps
Timing Detectors
Baseline: L-bar Quartic, Čerenkov detectors with sapphire and quartz radiators
Detector installation foreseen at the end 2015
Beam test results:
Time resolution: σ(t)=33 ps
4x5=20 3x3 mm2 bar elements
2+2 in-line modules: σ(t)~15 ps
Occupancy for m=50 pileup
High occupancy causes
inefficiency due to overlapping hits (may reach ~40%)

14. Timing Detectors
R&D on solid state detectors as future alternative solutions
Diamonds, LGADs, 3Ds
Motivations:
solid state detectors may have fine segmentation reducing the channel occupancy
detectors are thin and light, reducing nuclear interactions and allowing a large number of layers N
s(t)~1/sqrt(N)
state of the art for mip measurement: s(t)~100 ps
requires R&D to achieve s(t)~30 ps per layer
VERTEX Tracking at CT-PPS

15. VERTEX2014 - Tracking at CT-PPS
Summary
The joint CMS-TOTEM Proton Precision Spectrometer project will study Central Exclusive Production in p-p collisions, measuring the kinematic parameters of the scattered protons
To cope with CT-PPS requirements and challenges, new radiation-hard, slim-edge timing and tracking detectors are under development
Detector baseline: Čerenkov L-bar Quartic detectors for timing
3D silicon pixel detectors for tracking
Detector R&D:
Solid state timing detectors: Diamonds, Low Gain Avalanche
Diodes, 3D sensors
VERTEX Tracking at CT-PPS